A systematic method for diagnosing and improving soldering defects
By benchmarking analysis of the entire process and optimizing the equipment for tin spraying, the problem of recurring welding defects in the tin spraying process was solved, and the reliability and stability of welding were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANG XI XU SHENG DIAN ZI GU FEN YOU XIAN GONG SI
- Filing Date
- 2026-04-22
- Publication Date
- 2026-07-14
AI Technical Summary
The lack of systematic diagnostic methods in the current tin-plating process leads to repeated soldering defects, mismatch between process parameters and equipment functions, neglect of post-processing, lack of benchmark comparison and systematic improvement path, which affects soldering reliability.
Through benchmarking analysis of the entire process, upgrading of key equipment functions, and multi-parameter linkage optimization, bottlenecks are identified and improvement plans are generated, including equipment modification and parameter optimization, and standardized process packages are established.
It significantly improves the uniformity, cleanliness, and solderability of the tin plating layer, quickly locates and resolves soldering defects, is applicable to a variety of soldering problems, and ensures that the improvement results can be continuously replicated.
Abstract
Description
Technical Field
[0001] This invention relates to the field of printed circuit board manufacturing technology, and more specifically to a systematic method for diagnosing and improving soldering defects. Background Technology
[0002] Tin plating is a common surface treatment process for PCBs, and its quality directly affects the reliability of subsequent SMT soldering. Currently, the industry generally faces the following technical bottlenecks:
[0003] 1. One-sided problem diagnosis: When complex defects such as "poor soldering" or "raisin-like solder surface" occur, single variables such as solder pot temperature and flux type are usually adjusted in isolation. There is a lack of a comprehensive analysis of the entire process, from pretreatment cleanliness → flux activity and coverage uniformity → solder purity and solderability → post-treatment residue removal, which leads to repeated problems.
[0004] 2. Mismatch between process parameters and equipment functions: The existing production line equipment configuration (such as flux being only immersion type and post-treatment hot water washing without overflow) may not be able to support the execution of optimal process parameters, resulting in a disconnect between "having parameters but no means".
[0005] 3. Lack of benchmarking and systematic improvement path: For complex process defects, there is a lack of a methodology to quickly locate bottleneck processes and formulate systematic improvement plans that include equipment modification and parameter optimization by conducting detailed comparisons with benchmark production lines (such as Atelier Cologne) process by process and parameter by parameter.
[0006] 4. Post-processing is often overlooked: The cleaning effect of post-processing (hot water washing, brushing) is crucial for removing residual flux decomposition products and solder dross particles from the solder pad surface. Poor performance in this step is a major cause of "grape-like" solder surfaces (contamination leading to uneven wetting) and decreased solderability after storage, but it is often underestimated.
[0007] Therefore, there is an urgent need for a systematic and collaborative improvement method that runs through the entire tin-plating process to steadily improve the soldering reliability of tin-plated PCBs. Summary of the Invention
[0008] The purpose of this invention is to provide a systematic diagnosis and improvement method for tin-spraying soldering defects. Through full-process benchmarking analysis, key equipment function upgrades and multi-parameter linkage optimization, the uniformity, cleanliness and solderability of the tin-spraying layer can be fundamentally improved.
[0009] The technical solution of this invention is:
[0010] A systematic method for diagnosing and improving soldering defects includes the following steps:
[0011] Step S1: For the specific welding defects that occur, compare the production line with the welding defects with the benchmark production line that produces the same type of product, and perform a full process and parameter-by-parameter comparison.
[0012] Step S2: Based on the comparison results of Step S1, identify the key differences between the problem production line and the benchmark production line, and determine the key differences as the key bottlenecks leading to the specific welding defects. For each bottleneck, generate an improvement plan, which includes equipment modification suggestions and parameter optimization design.
[0013] Step S3: Based on the improvement plan generated in step S2, conduct multi-factor, phased testing and verification to determine the equipment configuration combination and optimized parameter combination that can effectively eliminate the specific welding defect.
[0014] Step S4: Based on the equipment configuration combination and optimized parameter combination determined in step S3, establish a standardized process package.
[0015] Furthermore, in step S1, the comparison of the entire process and each parameter includes:
[0016] The pretreatment process involves comparing parameters including micro-etching solution formulation, copper content, pretreatment brush configuration, and line speed.
[0017] The flux coating process involves comparing parameters including coating method, bath temperature control method, and flux type compatibility.
[0018] For the tin plating process, the parameters to be compared include the tin liquid temperature and copper content.
[0019] The post-processing steps include comparing parameters such as hot water washing temperature, whether there is an overflow function, whether defoamer is added, post-processing brush configuration, and drying temperature.
[0020] Further, in step S2, the key difference is identified as a critical bottleneck leading to the specific welding defect, and an improvement plan is generated, specifically including:
[0021] When the key bottleneck is the uniformity of flux coating, the improvement solution is to change the coating method to a combination of pressure spraying and immersion, and to install a constant temperature control system for the bath solution.
[0022] When the key bottleneck lies in the cleanliness of the post-treatment process, improvement solutions include: installing an overflow device for the hot water sink and prohibiting the addition of defoamers; and upgrading or repairing the brush configuration to ensure the brushes are in optimal condition.
[0023] When the key bottleneck lies in the pretreatment coarsening effect, the improvement solution is to optimize the matching relationship between the micro-etching solution concentration and the linear velocity.
[0024] Furthermore, in step S3, the multi-factor, phased testing and verification includes:
[0025] In the first phase, under the existing equipment conditions, the impact of changing the flux type was assessed on material compatibility.
[0026] The second phase involves implementing key equipment upgrades based on the first phase, and testing the effectiveness of the improvements.
[0027] In the third stage, based on the equipment modification, the associated parameters are optimized and the improvement effect is tested.
[0028] Furthermore, the test board at each stage simulates client conditions to assess welding reliability.
[0029] Furthermore, in step S4, the standardized process package includes:
[0030] Equipment configuration combinations, optimized combinations of process parameters, and key monitoring points and monitoring frequencies.
[0031] Furthermore, the specific welding defects include at least one of the following: incomplete soldering, grape-like tin surface, uneven tin thickness, and tin penetration.
[0032] Compared with existing technologies, the systematic diagnosis and improvement method for soldering defects provided by this invention has the following advantages:
[0033] I. The systematic diagnosis and improvement method for tin-plated soldering defects of this invention, by benchmarking against the entire process of a benchmark production line, can accurately locate the true bottleneck causing conformity soldering defects at the system level, avoiding the problem of "treating the symptoms rather than the root cause." The improvement solutions proposed for key bottlenecks, in addition to equipment modification and parameter optimization, solve the common industry problem of process parameters being unable to be implemented due to insufficient equipment capacity, achieving a thorough improvement through a combination of hardware and software. Multi-factor and multi-stage testing of the improvement solutions scientifically separates the individual effects of equipment modification and parameter adjustment, enabling rapid verification of the effectiveness of the improvement solutions and finding the optimal configuration combination. By establishing and implementing a standardized process package through the optimal configuration combination, the improvement results can be continuously replicated, preventing quality regression due to personnel changes or production negligence. Therefore, the systematic diagnosis and improvement method for tin-plated soldering defects of this invention can significantly improve the uniformity, cleanliness, and solderability of the tin-plated layer.
[0034] Second, the systematic diagnosis and improvement method for tin spraying defects of the present invention is not only applicable to solving the problems of "cold solder joints and grape-shaped tin surfaces", but its approach of benchmarking the whole process, identifying bottlenecks, and improving in an integrated manner can be applied to solving other quality defects in the tin spraying process (such as uneven tin thickness and tin penetration), and has wide applicability. Detailed Implementation
[0035] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below.
[0036] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0037] A systematic method for diagnosing and improving soldering defects includes the following steps:
[0038] Step S1: For the specific welding defects that occur, compare the production line with the welding defects with the benchmark production line that produces the same type of product, and perform a full process and parameter-by-parameter comparison.
[0039] Among them, the characteristic welding defects are cold solder joints, grape-like defects on the tin surface, uneven tin thickness, and tin penetration.
[0040] A comparison of the entire process and each parameter, including:
[0041] The pretreatment process involves comparing parameters including micro-etching solution formulation (sulfuric acid concentration, oxidant concentration), copper content, pretreatment brush configuration (mesh size, number of brush groups), and linear speed.
[0042] The flux coating process involves comparing parameters including coating method, bath temperature control method, and flux type compatibility.
[0043] For the tin plating process, the parameters to be compared include the tin liquid temperature and copper content.
[0044] The post-processing steps include comparing parameters such as hot water washing temperature, whether there is an overflow function, whether defoamer is added, post-processing brush configuration, and drying temperature.
[0045] Step S2: Based on the comparison results of Step S1, identify the key differences between the problem production line and the benchmark production line, and determine the key differences as the key bottlenecks leading to the specific welding defects. For each bottleneck, generate an improvement plan, which includes equipment modification suggestions and parameter optimization design.
[0046] The improvement plans include:
[0047] When the key bottleneck is the uniformity of flux coating, the improvement solution is to change the coating method to a combination of pressure spraying and immersion, and to install a constant temperature control system for the bath solution (including heating / cooling devices).
[0048] When the key bottleneck lies in the cleanliness of the post-treatment process, improvement solutions include: installing an overflow device in the hot water sink and prohibiting the addition of defoamers; and upgrading or repairing the brush configuration to ensure the brushes are in optimal condition.
[0049] When the key bottleneck lies in the pretreatment roughening effect, the improvement solution is to optimize the matching relationship between the micro-etching solution concentration and the linear velocity to ensure that over-etching is avoided while maintaining sufficient cleanliness.
[0050] Step S3: Based on the improvement plan generated in step S2, conduct multi-factor, phased testing and verification to determine the equipment configuration combination and optimized parameter combination that can effectively eliminate the specific welding defect.
[0051] This includes conducting multi-factor, phased testing and verification, including:
[0052] In the first phase, under the existing equipment conditions, only the flux type is changed (such as switching to lead-free special flux), and the impact of material compatibility is evaluated.
[0053] In the second phase, based on the first phase, key equipment modifications were implemented (such as adding flux spraying devices, improving post-treatment overflow devices, and repairing grinding brushes), and the improvement effects were tested.
[0054] In the third stage, based on the equipment modification, the associated parameters are optimized and the improvement effect is tested; the associated parameters refer to the parameters compared across the entire process in step S1.
[0055] In each stage, the test board simulates client conditions (such as reflow soldering) to evaluate soldering reliability and clarify the contribution of each improvement action to eradicating specific defects.
[0056] Step S4: Based on the equipment configuration combination and optimized parameter combination determined in step S3, establish a standardized process package.
[0057] Correspondingly, the standardized process package includes:
[0058] Equipment configuration combinations, such as a flux spraying device, a constant temperature control system (to control the flux temperature to be maintained at 35-41℃), a hot water washing overflow device, and a configuration of brush mesh size and number of groups.
[0059] Optimized combination of process parameters, such as sodium persulfate concentration of 80-120g / L for micro-etching, flux temperature of 35-41℃, and hot water washing temperature of 40-50℃ with no foaming.
[0060] Key monitoring points and monitoring frequency, such as analyzing micro-etching solution every shift, monitoring copper content in molten tin, and checking the quality of hot water washing.
[0061] By establishing and implementing standardized process packages with optimal configuration combinations, we can ensure that improvements can be continuously replicated and prevent quality regressions caused by personnel changes or production negligence.
[0062] The following detailed embodiments illustrate the systematic diagnosis and improvement method for soldering defects of the present invention.
[0063] Example 1
[0064] A systematic method for diagnosing and improving solder joint defects and grape-like defects on the tin surface in spray soldering includes the following steps:
[0065] Step S1, Benchmarking Analysis: Using Company A's production line as the benchmark, a full-process, parameter-by-parameter comparison is conducted with Company B's production line (the problematic production line). The comparison results show that the key differences between the two are:
[0066] Flux coating method: The benchmark production line uses a combination of spraying and immersion with constant temperature control; the problematic production line uses immersion without temperature control.
[0067] Post-treatment water washing: Benchmark production lines have overflow function and clean water quality; problem production lines have no overflow, produce a lot of foam, and need to add defoamer to remove the foam;
[0068] Post-processing brushes: Benchmark production lines use 2 sets of brushes with a mesh size of 1200; problem production lines use 1 set of brushes with a mesh size of 1000.
[0069] Step S2: Based on the comparison results of Step S1, the key differences are identified as the critical bottlenecks leading to cold solder joints and grape-like defects on the solder surface. Improvement solutions are generated for each bottleneck, as follows:
[0070] To address the bottleneck in flux coating methods, the improvement plan is to modify the coating method to a combination of pressure spraying and immersion, and to install a bath temperature control system (controlling the bath temperature to 35-41℃).
[0071] To address the bottleneck in post-treatment cleaning, the improvement measures include: installing an overflow device in the hot water washing tank and prohibiting the addition of defoamers; replacing the brushes with two sets of 1200-mesh brushes to ensure optimal brush performance.
[0072] Step S3, based on the improvement plan generated in step S2, conduct multi-factor, phased testing and verification to determine the equipment configuration combination and optimized parameter combination that can effectively eliminate the specific welding defect, specifically including:
[0073] In the first stage, the flux was changed from 809E (lead-containing) to 809T (lead-free), and the post-processing was kept as is to assess the impact of material compatibility.
[0074] In the second phase, based on the first phase, the post-processing equipment was modified in real time, including adding an overflow device and replacing the brushes, to verify the effect of improved cleanliness on eliminating "grape-like" defects.
[0075] In the third stage, after completing all equipment modifications, the flux bath temperature was further controlled at 35°C to verify the effect of constant temperature coating on improving flux activity, improving wettability, and reducing cold solder joints.
[0076] Step S4: Based on the equipment configuration combination and optimized parameter combination determined in step S3, establish a standardized process package, specifically including:
[0077] Equipment modification: Add flux spraying device and flux temperature control device, add overflow device for hot water washing, and use 2 sets of post-treatment grinding brushes with a mesh size of 1200.
[0078] Process parameter optimization: Use 809T flux and control the flux bath temperature at 35℃.
[0079] Through the above systematic improvements, a serious customer complaint (100% defective) was transformed into a set of replicable and preventable permanent process standards, significantly improving the robustness of the tin plating process and the soldering reliability of PCB products.
[0080] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.
Claims
1. A systematic method for diagnosing and improving defects in tin-sprayed soldering, characterized in that, Includes the following steps: Step S1: For the specific welding defects that occur, compare the production line with the welding defects with the benchmark production line that produces the same type of product, and perform a full process and parameter-by-parameter comparison. Step S2: Based on the comparison results of Step S1, identify the key differences between the problem production line and the benchmark production line, and determine the key differences as the key bottlenecks leading to the specific welding defects. For each bottleneck, generate an improvement plan, which includes equipment modification suggestions and parameter optimization design. Step S3: Based on the improvement plan generated in step S2, conduct multi-factor, phased testing and verification to determine the equipment configuration combination and optimized parameter combination that can effectively eliminate the specific welding defect. Step S4: Based on the equipment configuration combination and optimized parameter combination determined in step S3, establish a standardized process package.
2. The systematic diagnosis and improvement method for tin-spray soldering defects according to claim 1, characterized in that, In step S1, the comparison of the entire process and each parameter includes: The pretreatment process involves comparing parameters including micro-etching solution formulation, copper content, pretreatment brush configuration, and line speed. The flux coating process involves comparing parameters including coating method, bath temperature control method, and flux type compatibility. For the tin plating process, the parameters to be compared include the tin liquid temperature and copper content. The post-processing steps include comparing parameters such as hot water washing temperature, whether there is an overflow function, whether defoamer is added, post-processing brush configuration, and drying temperature.
3. The systematic diagnosis and improvement method for tin-spray soldering defects according to claim 1, characterized in that, In step S2, the key difference is identified as the critical bottleneck leading to the specific welding defect, and an improvement plan is generated, specifically including: When the key bottleneck is the uniformity of flux coating, the improvement solution is to change the coating method to a combination of pressure spraying and immersion, and to install a constant temperature control system for the bath solution. When the key bottleneck lies in the cleanliness of the post-treatment process, improvement solutions include: installing an overflow device for the hot water sink and prohibiting the addition of defoamers; and upgrading or repairing the brush configuration to ensure the brushes are in optimal condition. When the key bottleneck lies in the pretreatment coarsening effect, the improvement solution is to optimize the matching relationship between the micro-etching solution concentration and the linear velocity.
4. The systematic diagnosis and improvement method for tin-spray soldering defects according to claim 1, characterized in that, In step S3, the multi-factor, phased testing and verification includes: In the first phase, under the existing equipment conditions, the impact of changing the flux type was assessed on material compatibility. The second phase involves implementing key equipment upgrades based on the first phase, and testing the effectiveness of the improvements. In the third stage, based on the equipment modification, the associated parameters are optimized and the improvement effect is tested.
5. The systematic diagnosis and improvement method for tin-spray soldering defects according to claim 4, characterized in that, Each stage of the test board simulates client conditions to assess welding reliability.
6. The systematic diagnosis and improvement method for tin-spray soldering defects according to claim 1, characterized in that, In step S4, the standardized process package includes: Equipment configuration combinations, optimized combinations of process parameters, and key monitoring points and monitoring frequencies.
7. The systematic diagnosis and improvement method for tin-spray soldering defects according to any one of claims 1-6, characterized in that, The specific welding defects include at least one of the following: incomplete soldering, grape-like tin surface, uneven tin thickness, and tin penetration.